Method and device for the protection of refractory walls



Jan. 12, 1965 M. RlVlERE 3,165,301

MEITX'lOD AND DEVICE FOR THE PROTECTION OF REFRACTORY WALLS Filed OCT. 16. 1961 2 Sheets-Sheet 1 lllllll RE METHOD AND DEVICE FOR THE P RRRRRRRRRRRRRRRRRRRRRRRR L5 United States Patent 3,165,391 METHOD AND DEVICE FOR THE PRUTECTIGN 0F REFRACTORY WALLS Michel Riviere, Saint Germain-en-Laye, Seine-et-Gise,

France, assignor to Institut de Recherches tie la Siderurgie Francaise, Saint Germain-en-Laye, Seine-et-Qise, France Filed Get. 16, 1961, Ser. No. 145,157 Claims priority, application France, Oct. 18, 1960, 841,485, Patent 1,277,355 12 Claims. (Cl. 263-15) It is frequently desirable to create in modern industrial furnaces the highest possible temperature. The upper limit of the temperature in such industrial furnaces is frequently only limited by the heat resistance of the refractory material which forms the walls of the furnace.

The present invention is concerned with a method and device for the protection of refractory walls. More particularly, the present invention is directed to a method and device which'will protect refractory wall portions of industrial furnaces against heat radiation so that, due to such protection, the temperature in the furnace can be raised to a level higher than that at which the furnace could be operated without such protection of the refractory wall portion.

Since the productivity of the furnace and the production costs will improve in most cases when the temperature within the furnace can be raised, the present invention will result in an increase of the productivity and in a reduction of the production costs in a furnace equipped and operated in accordance with the present invention. Thereby it is usually of particular importance to protect the arched roof portion of the industrial furnace against excessive heat radiation.

It is therefore an object of the present invention to provide means for the protection of wall portions of such furnace so that due to such protection the furnace can be operated at a higher temperature.

It is another object of the present invention to provide such means for protecting wall portions of the furnace and thereby to prolong the useful life span of such wall portions.

It is a further object of the present invention to provide a method for protecting furnace wall portions against heat radiation.

Other objects and advantages of the present invention will become apparent from a further reading of the escription and of the appended claims.

With the above and other objects in view, the present invention contemplates in a horizontal furnace, in combination, an elongated furnace chamber including opposite end portions, a hearth portion located between said opposite end portions and a roof extending above the hearth portionfrom one of the opposite end portions to the other, burner means communicating with one of the end portions of the furnace chamber for forming a flame flowing along the hearth portion spaced from the roof towards the other of the opposite end portions, and means for forming a flow of a gaseous suspension of carbon particles flowing along the roof of the furnace chamber in the direction from the other of the opposite end portions towards the one end portion thereof, thereby protecting the roof against heat radiating from the flame formed by the burner means.

According to a preferred embodiment of the present invention, the furnace will comprise, in combination, an elongated furnace chamber including opposite end portions, a hearth portion located between the opposite end portions and a roof extending above the hearth portion from one of the opposite end portions to the other, burner means communicating with one of the end portions of the furnace chamber for forming a flame flowing alongthe hearth portion spaced from the roof towards the other of the opposite end portions, and fuel-introducing means including nozzle means located in the furnace chamber in the vicinity of the roof thereof at a distance from the one end portion equal to about three times the distance of the nozzle means from the other end portion of the furnace chamber for introducing into the furnace chamber adjacent to the roof thereof spaced further from the one end portion than from the other of the end portions a sheet of a fuel adapted to be cracked under formation of carbon particles at the temperature pevailing in the furnace chamber in the vicinity of the roof thereof when the furnace is in operation, so that a gaseous suspension of carbon particles will be formed upon introduction of the fuel into the operating furnace, the gaseous suspension flowing along the roof of the furnace chamber towards the one end portion thereof, thereby potecting the roof against heat radiating from the flame formed by the burner means.

The present invention also contemplates in the operation of a furnace of the type including afurnace chamber having opposite end portions, a hearth portion located between the opposite end portions and a roof extending above the hearth portion from one of the opposite end portions to the other, the steps of forming a flame flowing from one of the end portions towards the other of the end portions, the flame being spaced from the roof of the furnace chamber so that due to the flow of the flame, hot gas in the vicinity of the roof will be forced to flow in a direction opposite to the direction of flow of the flame; and introducing into the hot gas flow at a point farther distant from the one end portion than from the other of the end portions a fuel adapted at the temperature of the hot gas to be cracked under formation of carbon particles, the thus-formed carbon particles flowing suspended in the gas above the flame towards the one end portion, thereby protecting the roof of the furnace chamber against heat radiating from the flame, and the carbon particles then merging with the flame in the vicinity of the one end portion of the furnace chamber.

The transmission of heat between the heat source such as a flame or electric arc and the charge in the industrial furnace will occur simultaneously by radiation and convection, however, the transmission of heat from the heat source to the refractory wall portions which are not contacted by the heat source will take place nearly exclusively by radiation. Thus, for instance, the roof of an open hearth furnace is primarily exposed to heat radiating from the flame which is located in the furnace chamber spaced from the roof of the furnace.

According to the present invention, the heat exposure of the roof and/ or of other wall portions of an industrial furnace is reduced by interposing between such a wall portion and the source of heat a protective shield formed of a flowing suspension of carbon particles.

In hearth furnaces and open flame furnaces, for instance of the type of Martin furnaces, a stream of combus-tion products and fumes is formed which may be called a recirculating current and which originates at the side of the furnace which is opposite to the main burner forming the flame for melting, etc. of the charge. Such recirculating current will flow along the roof of the furnace in a direction opposite to that of the main flame. The recirculating current is composed of products of combustion having a high temperature. They are usually neutral or slightly oxidizing and the recirculating current flows at a low speed along the roof of the furnace in a direction from the tip of the main flame toward the burner nozzle at which the main flame originates.

According to the present invention, there is injected into an industrial furnace in which such a recirculating current of hot combustion products exists, parallel to the wall or the roof which is to be protected and close thereto, in a direction opposite to that of the main flame and concurrent with the recirculating current, into the same, a combustible hydrocarbon. Injection of the combustible hydrocarbon is carried out by means of an injector which will give the combustible hydrocarbon a slight momentum in the direction of the circulating current. The hydrocarbon which is thus injected into the hot recirculating current will be cracked therein under formation of carbon particles. The thus formed suspension of carbon particles in the recirculating current will flow along the wall orroof portion which is to be protected and will form a shield against radiation emanating from the main flame or electric arc, due to the factthat the heat absorption factor of such suspension of carbon particles is high and the flow of the same in the recirculating current is at a low speed. i

The present invention may be carried out by the injection of a liquid or gaseous combustible hydrocarbon, or by the introduction of a finely subdivided highly viscous or nearly solid hydrocarbon such as heavy fuel oil or tar. Preferably, particularly when a gaseous hydrocarbon is introduced into the recirculating current, a hydrocarbon gas will be chosen which includes a relatively large proportion of carbon atoms in its molecule. 7

The injecting means for the hydrocarbon may be conventional injectors having a nozzle from which a conical jet stream of the hydrocarbon will be introduced into the recirculating current, or, the nozzle may be so formed as to produce a sheet-like stream of hydrocarbon, panallel to and preferably of substantially the same width as the roof portion which is to be protected.

The protective shield or sheet which is thus formed for the purpose of protecting the adjacent wall portions against radiation heat emanating from a heat source farther distant from the wall portion than the protective sheet, will be formed by a cloud of carbon particles, or by a suspension of carbon particles in the'recirculating current, which carbon particles have been formed by cracking of injected hydrocarbons, but have not yet been oxidized so as to form a gaseous combustion product. Due to the fact that the recirculating current is either formed of non-oxidizing gas or of only slightly oxidizing gas, further combustion of the carbon particles whichare carried along by the recirculating current will not occur or will only occur to a very slight degree which does not seriously interfere with the formation of the protective shield. In order to accomplish the foregoing, it is important that the hydrocarbon is injected at low speed into the hot and only slightly oxidizing zone of, the furnace approximately where the recirculating current originates and that the speed'of the current is sufficiently slow to pen mit for cracking of the hydrocarbon and formation of carbon particles in the vicinity of the roof or wall portion to be protected which is farthest from the origin of the flame so that the carbon particles will then flow along such wall portion'towards the area of origin of the flame thereby forming a protective shield interposed between such 'wall or roof portion and the flame. As stated above, it is also important that the carbon particles while flowing along the wall or roof portion which is to be protected are not subjected to such a degree of combustion that an appreciable reduction in the number or size of the carbon particles will occur. To comply with this condition is possible due to the relatively small oxygen content of the recirculating current.

According to the present invention it is possible to protect refractory wall or roof portions of the furnace not only against heat radiation emanating from a flame or are but also against the heat radiation emanating from the liquid bath after the charge in the furnace has been melted. This is particularly important in cases where the surface of the liquid bath in the furnace possesses an from burner 4a.

of oil is introduced through conduit 11a.

7 4 increased deflecting power such as is present for instance in the. case of steel forming furnaces wherein so-called shining slag is formed, or also in' glass furnaces or furnaces used for the refining of copper.

The novel features which are considered l'dS characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following descriptionof specific embodiments when read in connection with the taccornpanying drawing, in which: 7 V

FIG. 1 is a cross sectional elevational schematic view of a furnace.arrangementaccordiug to the present in vention; and 7 FIG. 2 is a fragmentary perspective view of one end portion of a hearth furnace of refractory brick shown in new condition and illustrating the arrangement of the hydrocarbon injecting means.

Describing the invention now with reference to the drawing, the process of the present invention: may be carried out, for instance, in a Martin furnace of tons capacity, heated with heavy fuel-oil. The furnace comprises in conventional manner a hearth 1, a roof 2, a furnace chamber 3, as well as the principle or main burners 4a and 41) at opposite ends of the furnace chamber. Oil is introduced through the main injectors 5a and 5b and the combustion air is preheated in conventional recuperators 6a and 6b. As illustrated inFlG. 1, a liquid metal charge 7 is located on hearth 1.

As illustrated in FiGURE 1, main flame 8 emanates At the opposite end of the furnace, recirculating currents originate and circulate with moderate speed along the furnace roof until they return to the main current of the flame in the vicinity of the operating burner 4a. These recirculating currents are composed of gaseous combustion products of high temperature and low oxygen content and are indicated in FIG- URE 1 by arrow with the indicia The current flow is indicated as it occurs when burner 4a, i.e. the left hand burner is operating. Obviously, the direction of the recirculating current is reversed when instead of burner 4a., burner 4b produces the -flame.' As illustrated, burner 4a is operative'and burner 4b is inoperative.

Injectors 9a andf9b cross-sect the roof of the furnace and are arranged in pairs so that one pair of injectors is three times farther; from the end of the furnace roof located adjacent to burner 4a than from the end of the furnace roof located adjacent to burner 4b, while the position'of the other pair of injectors is reversed, i.e. closer to burner 4a than to burner 4b.

Fuel-oil is fed into injectors 9a through conduits 10a while compressed air, forming a finely subdivided spray In a conventional manner, not illustrated in detail, cooling water is introduced and'withdrawn through conduit 12a. Burners 9b are similarly provided with means for introducing oil,

compressed air and for circulating cooling water as indicatcdby reference numerals 10b, 11b and 1212.

FIGURE 2 showsa simplified fragmentary perspective view of the right upper portion of the furnace including the pair of injectors 9a and the manner in which the same cross sect :the furnace roof. 7

Each of the injectors 9a and 9b terminates in a nozzle having a reduced cross section of about 2.5 mm. diameter and is arranged about 20 centimeters from and below the inner well surface of the surface, roof,"so asto project fromithe nozzle orifice a finely subdivided jet or stream of oil in a direction parallel to the roof, into recirculating current 1, in a direction opposite tothat of main flame 8. The fine distribution of the oil is accomplished bythe introduction of compressed air under a pressure of about 5 atmospheres. The amount of air for distributing the oil is kept as low as possible in order to limit the amount of oxygen which isthus introduced into the recirculating current. For each injector, the thrust is in the neighborhood of 0.25 kg. per million of kcal, although the conventional amount for metallurgical burners is about 2 kg. per million kcal. The amount of air for spraying the oil equals about 200 g./h. per kg./h. of oil, although in conventional burners about 1 kilogram of air is generally used per kilogram of oil.

The injectors 9a and 9b operate in pairs in such a manner that oil is injected into the pair which is further distant from the burner from which at that time the main or principle flame emanates. Each pair of injectors 9a or 9b, whichever is operating at the time, is supplied with oil jointly with the opposite main burner, i.e. jointly with the burner which at that time provides the main flame. For instance, oil is simultaneously fed to burner 4a and injectors 9a, so that at the moment when the flame emanating from the burner 4a is extinguished by cutting off the fuel supply to conduit 5a, the supply of oil to the pair of injectors 9a is also terminated. On the other hand, when the new flame is then formed at burner 4b, oil will be simultaneously introduced through injectors 9b.

The cracking of the oil and the formation of carbon particles starts at a distance of about to centimeters from the injector nozzle. The injectors are so positioned that the carbon particles formed by cracking are carried along at low speed with the recirculating current. The elevated temperature of the recirculating current facilitates the cracking of the oil, while the small oxygen content of the gaseous suspension of carbon particles, thus formed, and the low speed thereof will retard the combustion of the carbon particles formed by cracking of the hydrocarbon and thus will allow the formation of a protective dense opaque stream or shield 13 which will flow along the roof interposed between flame 8 or charge 7 I on the one hand and roof 2 on the other hand. The cracking products such as carbon particles will eventually merge with the main flame in the vicinity of burner 4a, i.e. in the vicinity of the burner from which the main flame emanates at that time and will then be subjected to complete combustion in the main flame.

Preferably, the pairs of injectors 9a and 9b are not located at the extreme ends of the furnace space but somewhat towards the center thereof, approximately as illustrated, i.e. approximately and 75% respectively distant from the two burners, for reasons of backwash and of the geometrical configuration of the sheet-like recirculating stream in which otherwise a premature disappearance of the cloud of carbon particles would occur. On the other hand, since the roof of the furnace is more curved at its end portions than at its center portions, it is also more fragile in this area and thus it would be undesirable to weaken the curved end portions of the furnace roof by having the injectors penetrate through the curved end portions. Furthermore, the end portions of the furnace roof are less exposed to heat than the central portion of the furnace roof and in view of all of these considerations, it was found desirable to space the injectors from the extreme ends of the furnace spaced at a distance of about one-quarter of the total length of the furnace space or roof. This represents a satisfactory solution for the above discussed considerations and will protect particularly the center portion of the furnace roof, i.e. the portion thereof which is most exposed to high temperature.

The total amount of oil which is introduced into the furnace equals 1,000 kg./h. and this total amount is maintained constant, however, the proportion thereof which is introduced through the injectors 9a or 9b may vary between about 100 and 250 kg./h., equal to between 10% and 25% of the total amount of fuel introduced into the furnace.

A very great number of tests have been carried out within the above range of introducing between 10 and 25% of the total fuel supply through injectors such as injectors 9a and 9b, and it has been found that within this range optimum results are achieved with respect to lowering of the temperature of the roof. However, special conditions may exist which would require to deviate from the range of between 10 and 25% fuel introduction through the injectors penetrating the furnace roof. It seems that the greater the relative amount or percentage of fuel which is injected through injectors 9a or 9b, the greater will be the decrease of the temperature of the roof so that it sometimes might be advisable to introduce through the injectors even more than 25 of the total fuel and accordingly less than 75% of the fuel will then be introduced through main burners 4a or 4b.

The sheet-shaped suspension of carbon particles which is produced of the hydrocarbons introduced through injectors 9a and 9b into the recirculating currents 1, will unfold underenath the roof of the furnace, flow slowly along the roof towards the operating main burner and will then be sucked into the main flame 8. In main flame 8, the combustible contents of the recirculating current, i.e. mainly the carbon particles, and hydrogen will then be completely oxidized. Even by increasing the percentage of the total fuel which is introduced through injectors 9a or 91), it has been found that all of the combustible material carried along with the recirculating current will be completely burned in main flame 8. This is proven by the fact that even at a very high percentage introduction of oil through injectors 9a or 9b, no combustible material could be found in the flue gases leaving the furnace. As described hereinabove, a reduction of the temperature of the roof is achieved which in the center portion thereof, i.e. in the portion of the roof which is best protected or covered by the cloud of carbon particles, will amount to between 40 and 50 C.

In open hearth furnaces, it is particularly advantageous to carry out the process of the present invention from the time of fusion of the scrap iron until the end of the tapping, because during this entire time period there is a stable flow of recirculating cur-rent and thus a stable and even protective shield will be formed of the suspension of carbon particles in the recirculating current, which flow will be free of any interruption and disturbance and thus capable of giving an even protection to the roof. It is also possible to operate in accordance with the present invention during the charging of the furnace and prior to completion of the melting of the scrap, however, during these early stages of the furnace operation, the conditions for carrying out the invention, i.e. the conditions for maintaining an even and effective shield of suspended carbon particles in the vicinity of the roof, are less favorable,

It will be understood that each of the elements de scribed above or two or more together, may also find a useful application in other types of furnaces differing from the types described above.

While the invention has been illustrated and described as embodied in an open hearth furnace, it is not intended to be limited to the details shown, since various modiflcations and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and arcintended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed and desired to be secured by Letters Patent is:

1. In a horizontal furnance, in combination, an elongated furnace chamber including opposite end portions, 21 hearth portion located between said opposite end porone of said opposite end portions to the other; burner means communicating with one of the end portions of said furnace chamber for forming a flame flowing along said hearth portion spaced from said roof towards the other of said opposite end portions; gas outlet means at the other of said end portions of said furnace chamber permitting escape of hot gases from said chamber without .reaching the region of said furnace chamber adjacent to the roof thereof; and fuel-introducing means for independently-of said burner means introducing into said furnacechamber intosaid region adjacent to the roof thereof spaced further from said one end portion than from the other of said end portions a carbonaceous fuel adapted to be cracked under liberation of free carbon particles at the temperature prevailing in said furnace chamber in said region adjacent to said roof thereof when said furnace is in operation, so that gaseous suspension of carbon particles :will be formed upon introduction of said fuel into the operating furnace, said gaseous suspension flowing first in said region adjacent to the roof of said furnace chamber towards said one end portionthereof in countercurrent to the direction of flow of said flame from said burner to said outlet opening, between the same and the roof of said furnace chamber and then downwardly to said flame to be burned therein while flowing towards said other of said opposite end portions, thereby protecting said roof against heat radiating from said flame formed by said burner means.

2. In a furnace, in combination, an elongated furnace chamber including opposite end portions, a hearth portion located between said opposite end portions and a roof extending above said hearth portion from one of said opposite end portions to the other; burner means communicating with one of the end portions of said furnace chamber for forming a flame flowing along said hearth portion spaced from said roof towards the other of said opposite end portions; gas outlet means at the other of said end portions of said furnace chamber permitting escape of hot gases from said chamber without reaching the region of said furnace chamber adjacent .to the roof thereof; and.

fuel-introducing means including nozzle means located in said furnace chamber into said region adjacent to said roof thereof at a distance from said one end portion equal to about three times the distance of said nozzle means from the other end portion of said furnace chamber for independently of said burner means introducing into said furnace chamber adjacent to the roof thereof spaced further from said one end portion than from the other of said end portions a carbonaceous fuel adapted to be cracked under liberation of free carbon particles at the temperature prevailing in said furnace chamber in said region adjacent to said roof thereof when said furnace is in operation, so that a gaseous suspension of carbon particles will'be formed upon introduction of said fuelinto the operatingv furnace, said gaseous suspension flowing first in said region adjacent to the roof of said furnace chamber towards said one end portion thereof in countercurrent to the direction of flow of said flame from said burner to said outlet opening, between the same-and the 'roof of said furnace chamber and then downwardly to said flame to be burned therein while flowing towards said other of said opposite end portions, thereby protecting said'roof against heat radiating from said flame formed by said burner means.

3. In a furnace, in combination, an elongated furnace chamberincluding opposite end portions, a hearth portion located between said opposite end portions and a roof extending above said hearth portion from one of said opposite end portions to the other; burner means communi- -eating with one 'of the end portions of said furnace chamber for forming a flame flowing along said hearth portion end portions; gas outlet means at the other of said end portions of said furnace chamber gases from said chamber without. reaching the region of said furnace chamber adjacent to thereof thereof; and fuel-introducing means including nozzle means located in said furnace chamber into said region adjacent. to said roof thereof atja distance from said one endv portion equal to about three times the distance of said nozzle means from the other end portion ofsaid furnace chamber for independently of said burner means introducing into said furnace chamber adjacent to the roof thereof spaced further from said one end portion than fromthe other of said end portions a conical stream of a carbonaceous fuel adapted to be cracked under liberation of free carbon particles at the temperature prevailing in said furnace chamber in said region adjacent to said roof thereof when said furnace is in operation, so that a gaseous suspension of carbon particles will be formed upon introduction of said fuel into the operating furnace, said gaseous suspension flowing first in said region adjacent to the roof of said furnace chamber towards said one end portion thereof in counter current to the direction of flow of said flame from said burner to said outlet opening, between the same and the roof of said furnace chamber and then downwardly to said flame to be burned therein while flowing towards said other of said opposite end portions, thereby protecting said roof against heat radiating from said flame formed by said burner means.

4. in a furnace, in combination, an elongated furnace chamber including opposite end portions, a hearth portion located between said opposite end portions and a roof extending above said hearth portion from one of said opposite end portions to the other; burner means communicating with one of the endportions of said furnace chamber for forming a flame flowing along said hearth portion spaced from said roof towards the other of said opposite end portions; gas outlet means at the other of said end portions of said furnace chamber permitting escape of hot gases from said chamber without'reaching the region of said furnace chamber adjacent to the roof thereof;

and fuel-introducing means including nozzle means 'end portion equal to about three times the distance of said nozzle means from the other end portion of said furnace chamber for independently of said burner means introducing into said furnace chamber adjacent to the roof thereof spaced further from said one end portion than from the other of said end portions a sheet of a carbonaceous fuel adapted to be cracked underliberation of free carbon particles at the temperature prevailing in said furnace chamber in said region adjacent to said roof thereof when said furnace is in operation, so that'a gaseous suspension of carbonparticles will be formed upon introduction of said fuel into the operating furnace,1said gaseous suspension flowing first in said region adjacent to the roof of said furnace chamber towards said one end portion thereof in countercurrent to the direction of flow of said flame from said burner to said outlet opening, between the same and the roof of said furnace chamber and then downwardly to saidflame to be burned therein while flowing towards said other of'said opposite end portions, thereby protecting said roof against heat radiating'frorn said flame formed by said burner means.

,5. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a

a hearth located between said opposite end portions and a roof extending above said hearth fromone of said opposite end portions to the-other, the steps of forming a flame flowing through one of saidopen end portions into .said furnace chamber towards the opposite open end porpermitting escape of hot 9 opposite to the direction of flow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a point farther distant from said one end portion than from the other of said end portions a carbonaceous fuel adapted at the temperature of said hot gas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof of said furnace chamber against heat radiating from said flame, and said carbon particles then merging with said flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other a of said opposite end portions.

6. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a hearth located between said opposite end portions and a roof extending above said hearth from one of said opposite end portions to the other, the steps of forming a flame flowing through one of said open end portions into said furnace chamber towards the opposite open end portion so that a large proportion of the hot gases emanating from said flame will directly flow out from said furnace chamber through said other open end portion thereof and the remaining small proportion of said hot gases will be forced in the vicinity of said roof to flow in a direction opposite to the direction of flow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a point about three times farther distant from said one end portion than from the other of said end portions a fluid carbonaceous fuel adapted at the temperature of said hot gas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof of said furnace chamber against heat radiating from said flame, and said carbon particles then merging with said flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other of said opposite end portions.

7. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a hearth located between said opposite end portions and a roof extending above said hearth from one of said opposite end portions to the other, the steps of forming a flame flowing through one of said open end portions into said furnace chamber towards the opposite open end portion so that a large proportion of the hot gases emanating from said flame will directly flow out from said furnace chamber through said other open end portion thereof and the remaining small proportion of said hot gases will be forced in the vicinity of said roof to flow in a direction opposite to the direction of flow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a point farther distant from said one end portion than from the other of said end portions a hydrocarbon fuel adapted at the temperature of said hot gas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof of said furnace chamber against heat radiating from said flame, and said carbon particles then merging with said flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other of said opposite end portions.

8. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a hearth located between said opposite end portions and a roof extending above said hearth from one of said opposite end portions to the other, the steps of forming a flame flowing through one of said open end portions into said furnace chamber towards the opposite open end portion so that a large proportion of the hot gases emanating from said flame will directly flow out from said furnace chamber through said other open end portion thereof and the remaining small proportion of said hot gases will be forced in the vicinity of said roof to flow in a direction opposite to the direction of flow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a point farther distant from said one end portion than from the other of said end portions a liquid hydrocarbon fuel adapted at the temperature of said hot gas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof of said furnace chamber against heat radiating from said flame, and said carbon particles then merging withsaid flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other of said opposite end portions.

9. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a hearth located between said opposite end portions and a roof exending above said hearth from one of said opposite end portions to the other, the steps of forming a flame flowing through one of said open end portions into said furnace chamber towards the opposite open end portion so that a large proportion of the hot gases emanating from said flame will directly flow out from said furnace chamber through said other open end portion thereof and the remaining small proportion of said hot gases will be forced in the vicinity of said roof to flow in a direction opposite to the direction of flow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a point farther distant from said one end portion than from the other of said end portions a carbonaceous fuel consisting essentially of gaseous hydrocarbon molecules including a large proportion of can bon atoms and adapted at the temperature of said hot gas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof of said furnace chamber against heat radiating from said flame, and said carbon particles then merging with said flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other of said opposite end portions.

10. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a hearth located between said opposite end portions and a roof extending above said hearth from one of said opposite end portions to the other, the steps of forming a flame flowing through one of said open end portions into said furnace chamber towards the opposite open end portion so that a large proportion of the hot gases emanating from said flame will directly flow out from said furnace chamber through said other open end portion thereof and the remaining small proportion of said hot gases will be forced in the vicinity of said roof to flow in a direction opposite to the direction of flow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a point farther distant from said one end portion than from the other of said end portions finely subdivided tar as a carbonaceous fuel adapted at the temperature of said hot gas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof of said furnace chamber against heat radiating from said flame, and said carbon particles then merging with said flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other of said opposite end portions.

11. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a hearth located between said opposite end portions and a roof'extending above said hearth from one of said opposite end portions to the other, the steps of forming a flame flowing through one of said open end portions into said furnace chamber towards the opposite open end portion so that a large proportionof the hot gases emanating from said flame will directly flow out from said furnace chamber through said other open end portion thereoi and the remaining. small proportion of said hot gases will be forced in the vicinity of said roof to flow in a direction opposite to the direction, of flow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a point farther distant from said one end portion than from the other of said end portions finely subdivided heavy fuel-oil as a carbonaceous fuel adapted at the temperature of said hot gas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof'of said furnace chamber against heat radiating from said flame, and said carbon particles then merging with said flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other of said opposite end portions.

12. In the operation of a furnace of the type including a furnace chamber having opposite open end portions, a hearth located between said opposite end portions and a roof extending above said hearth from one of said opposite end portions to the other, the steps of forming a flame flowing through one of said open end portions into said furnace chamber towards the opposite open end portion so that a large proportion of'the hot gases emanating from said flame will directly flow out'from said furnace chamber throughrsaid other open end portion thereof and the remaining small proportion of said hot gases-will be forced in thevicinity of said roof to flow in a direction opposite to the, direction ofrflow of said flame; and introducing into said remaining forced hot gas flow in the vicinity of the roof at a pointfarther distant from said one end portion than from the other of said end portions a gaseous hydrooarbon fuel adapted at the temperatureof said hotgas to be cracked under liberation of free carbon particles, the thus-formed carbon particles flowing first suspended in said gas above said flame towards said one end portion, thereby protecting the roof of said furnace chamber against heat radiating from said flame, and said carbon particles then merging with said flame in the vicinity of said one end portion of said furnace chamber to be completely burned therein while flowing toward the other of said opposite end portions. 0

References Cited by the Examiner UNITEDVSTATES PATENTS 4/56 Great Britain.

CHARLES SUKALO, Primary Examiner.

PERCY L. PATRICK, Examiner. 

5. IN THE OPERATION OF A FURNACE OF THE TYPE INCLUDING A FURNACE CHAMBER HAVING OPPOSITE OPEN END PORTIONS, A A HEARTH LOCATED BETWEEN SAID OPPOSITE END PORTIONS AND A ROOF EXTENDING ABOVE SAID HEARTH FROM ONE OF SAID OPPOSITE END PORTIONS TO THE OTHER, THE STEPS OF FORMING A FLAME FLOWING THROUGH ONE OF SAID OPEN END PORTIONS INTO SAID FURNACE CHAMBER TOWARDSA THE OPPOSITE OPEN END PORTION SO THAT A LARGE PROPORTION OF THE HOT GASES EMANATING FROM SAID FLAME WILL DIRECTLY FLOW OUT FROM SAID FURNACE CHAMBER THROUGH SAID OTHER OPEN END PORTION THEREOF AND THE REMAINING SMALL PROPORTION OF SAID HOT GASES WILL BE FORCED IN THE VECINITY OF SAID ROOF TO FLOW IN A DIRECTION OPPOSITE TO THE DIRECTION OF FLOW OF SAID FLAME; AND INTRODUCING INTO SAID REMAINING FORCED HOT GAS FLOW IN THE VINCINITY OF THE ROOF AT A POINT FARHTER DISTANT FROM SAID ONE END PORTION THAN FROM THE OTHER OF SAID END PORTIONS A CARBONACEOUS FUEL ADAPTED AT THE TEMPERATURE OF SAID HOT GAS TO BE CRACKED UNDER LIBERATION OF FREE CARBON PARTICLES, THE THUS-FORMED CARBON PARTICLES FLOWING FIRST SUSPENDED IN SAID GAS ABOVE SAID FLAME TOWARDS SAID ONE END PORTION, THEREBY PROTECTING THE ROOF OF SAID FURNACE CHAMBER AGAINST HEAT RADIATING FROM SAID FLAME, AND SAID CARBON PARTICLES THEN MERGING WITH SAID FLAME IN THE VICINITY OF SAID ONE END PORTION OF SAID FURNACE CHAMBER TO BE COMPLETELY BURNED THEREIN WITH WHILE FLOWING TOWARD THE OTHER OF SAID OPPOSITE END PORTIONS. 